Cooking stoves that use natural gas or propane fuel typically have several burners below cook-top grills and individual controllers for flame height and heat output. Electric cooking stoves have resistive heating elements that radiate heat by converting electric current supplied to them. Controls have become essentially standardized with removable knobs on the end of heat-source control shafts, the rotation of which controls the amount of gas flow and, therefore, flame height and heat output; or in the case of electric stove, the amount of electric current converted to heat.
At one rotation point, there is no further rotation allowed and the gas supply or electric current is cut off. At the opposite rotation points gas flow or electric current is on and the amount of heat is determined by heat-source shaft rotation position.
Turning gas flow or electric current on or off is a manual process that requires a user to be present for either action. Currently, there are no safety features that will automatically turn off a burner's gas supply, or an electric stove's heat element current, based on time duration. Therefore, it is possible that a control may inadvertently be left with gas supply or electric current turned on causing at a minimum burning of food and cookware; and worst-case, causing fire and destruction of property and even lives.